1. Field of the Invention
The invention relates to the field of lifts for assisting wheelchair users in entering and exiting vehicles, for example through the sliding side door or rear door of a van. The invention provides a foldable platform lift, rotatably mounted on a vertical post, and including a drive means enabling vertical and rotational displacement of the platform on the post. According to the invention, the vertical post is displaceable laterally of the vehicle on a linear drive having a stroke sufficient to position the vertical post clear of the doorway, for clearance to lower and rotate the platform. The combination of vertical and lateral horizontal movement with pivoting on the vertical post provides a compact arrangement that does not limit the user's ability to enter and exit the platform to any particular angle relative to the longitudinal axis of the vehicle.
2. Prior Art
According to U.S. Pat. No. 4,664,584--Braun et al, a wheelchair lift for a van is provided with a horizontal platform mounted at one corner to the lower end of a telescoping vertical drive post carrying a hydraulic actuator for moving the horizontal platform vertically up and down between the ground and the level of the floor of the passenger compartment. The apparatus is mounted to the floor of the van inside a sliding side door. The movable parts of the lift, namely the platform and the vertical drive post, hinge around a fixed vertical pivot post that is rigidly mounted just inside the van at the edge of the doorway. The wheelchair is rolled onto the platform inside the van; the platform is rotated outwardly on the fixed pivot post; the platform is lowered to the ground; and the wheelchair is rolled off.
The lift must be mounted such that it can be moved completely inside the vehicle, allowing the door to be closed. The vertically displaceable parts likewise must be movable completely outside, for clearance to lower the platform. In Braun, the telescoping vertical drive post is spaced radially from the fixed pivot post. Therefore, when the platform and vertical drive post are rotated around the fixed pivot axis, they move in an arc through the vehicle doorway. In this manner, the platform can be moved in and out of the van and when the platform is outside of the van, the vertical drive post is clear of the doorway for lowering the platform.
The platform and vertical drive can hinge or pivot through 90.degree.. The platform remains horizontal. When the platform is inside the van, the user moves on or off the platform in a direction perpendicular to the longitudinal axis of the vehicle. When the platform is outside the van the user moves on or off the platform in a direction parallel to the longitudinal axis of the vehicle. This arrangement is effective for moving the vertically displaceable parts of the lift through the van doorway in either direction, with clearance when outside. However, since hinging around the fixed vertical pivot is the aspect that moves the platform through the doorway of the van, there is no choice for the angle of the platform when outside and lowered. The platform cannot be hinged to another angle when lowered, due to interference with the vehicle. In addition, the platform takes up a good deal of space in the van, requiring persons without wheelchairs to climb over the platform to use the doorway.
A different form of van mounted wheelchair lift is disclosed, for example, in U.S. Pat. No. 4,353,436--Rice et al. According to this arrangement, a linearly displaceable track and roller arrangement moves two vertically telescoping drive posts on opposite sides of the vehicle doorway, into the van or out of the van. When the drive posts are clear of the doorway, the platform can be lowered. In this case the user must move onto and off of the platform in a direction perpendicular to the longitudinal axis of the vehicle. Again, there is no choice of access angle.
It is also the case with ramp structures that the access angle is fixed, for example as in U.S. Pat. No. 4.966,516--Vartanian. Typically the ramp is directed perpendicular to the doorway, or laterally of the vehicle for the side door. According to Vartanian '516, the ramp can have alternative pivots so that at least when stowed away, the ramp does not interfere with passage through the doorway.
A lift generally occupies less space than a ramp when deployed. When embarking or disembarking a vehicle, it may be desirable at times to move parallel to the vehicle axis, perpendicular to the axis or at some other angle. For example, to move onto or off of a lift or ramp between parked cars or at a driveway, perpendicular to the vehicle axis is the preferred direction. If the van is alongside another vehicle, for example when in a parking lot or when double parked parallel to the vehicle axis is preferred. In other situations, such as near obstructions or when the doorway opens into a traffic lane or if the ground is sloped, some other angle may be more direct or even may be required to provide sufficient space to maneuver the wheelchair.
It would be advantageous to provide a wheelchair lift structure that has all the advantages of the foregoing cited patents, without the drawbacks of their respective structures. It would be particularly advantageous to provide a compact wheelchair lift that does not use a great deal of interior space or obstruct the doorway, that enables some choice of access angle, and that is durable and versatile.